Answer: Johnson grass is a perennial weed. It is the most difficult weed to control because it has perennial roots and needs to be spot treated with a vegetation killer such as Round-Up. Round-Up will kill anything it touches, so be careful when using it. Simply target each weed and spray it with Round-Up. You can protect the other plants in the bed by setting a cardboard box over it when you spray the weeds. Round-Up will travel down to the roots of the weed but it won't translocate in the soil so your other plants should be safe.
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